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Red sky in the morning, or grey sky to the west in the evening, indicate storms are on the way. Red sky in the evening, or grey sky to the east in the morning, indicate storms have likely passed.
Night sky
Post-Collapse, there won't be great deal of light pollution from the planet surface from things like street lights, office blocks, etc. As such, the night sky will be dark, in the 1-3 range on the following diagram (from stellarium):
The band will be chosen as follows:
- Urban - 3 (heavy dust in the atmosphere)
- Arizona - 2 (dust in the atmosphere)
- Rockies - 1 (clean mountain air)
An alternate mechanism could be to select a band based on the number of base structures on the map.
Higher bands will be applied based on the presence of certain types of cloud (eg. Nimbostratus, Cirrostratus), fog or mist, but without the glow that would be associated with man-made light sources.
Cold is the night, when the stars shine bright.